Process for reducing 3,3,3-trifluoropropyne in 2,3,3,3-tetrafluoropropene

Abstract

This application relates to a method for reducing 3,3,3-trifluoropropyne in 2,3,3,3-tetrafluoropropylene. The invention relates to a method for reducing the concentration of fluorinated alkyne impurities, such as 3,3,3-trifluoropropyne (TFPY), in 2,3,3,3-tetrafluoropropylene (HFO-1234yf), comprising contacting such a mixture with a caustic material, such as sodium hydroxide (NaOH), under conditions that effectively reduce the concentration of fluorinated alkyne impurities, and in some practices including reducing the concentration by at least about 50%.

Description

[0001] This application is a divisional application of the invention patent application filed on November 2, 2017, with application number 201780068375.3 and entitled "Method for reducing 3,3,3-trifluoropropyne in 2,3,3,3-tetrafluoropropylene". Technical Field

[0002] This invention provides a method for reducing fluorinated alkyne impurities in 2,3,3,3-tetrafluoropropene (HFO-1234yf) using caustic materials. In one embodiment, using a caustic material, such as sodium hydroxide (NaOH), the content of TFPY (3,3,3-trifluoropropyne) impurities is reduced to less than 100 ppm. Background Technology

[0003] Hydrofluoroolefins (HFOs), such as tetrafluoropropylene, including 2,3,3,3-tetrafluoropropylene (HFO-1234yf), are known to be effective refrigerants, heat transfer media, propellants, foaming agents, gaseous dielectrics, bactericide carriers, polymerization media, particulate removal fluids, carrier fluids, polishing abrasives, displacement desiccants, and power cycle working fluids. Unlike chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) (both of which potentially damage the Earth's ozone layer), HFOs pose no threat to the ozone layer. HFO-1234yf has also been shown to be a low-global warming compound with low toxicity, thus meeting the increasingly stringent requirements for refrigerants in mobile air conditioning. Therefore, compositions containing HFO-1234yf are a promising material for developing applications in many of the aforementioned fields.

[0004] One method for preparing HFO-1234yf uses 1,1,2,3-tetrachloropropene (1230xa) as a starting material. The method includes the following three steps:

[0005] Step (1) In a gas-phase reactor containing a solid catalyst, 1230xa + 3HF --> 2-chloro-3,3,3-trifluoropropene (1233xf) + 3HCl;

[0006] Step (2) In a liquid-phase reactor containing a liquid catalyst, 1233xf + HF --> 2-chloro-1,1,1,2-tetrafluoropropane (244bb); and

[0007] Step (3) In the gas phase reactor, 244bb --> 1234yf + HCl.

[0008] In step (3), the final product—2,3,3,3-tetrafluoropropene (1234yf)—is typically contaminated with fluorinated organic byproducts, such as fluorinated alkynes. These fluorinated alkynes include fluorinated propynes, such as 3,3,3-trifluoropropyne (TFPY). Since both TFPY and 1234yf are light components with relatively low boiling points, conventional purification methods, such as distillation, result in significant yield losses of 1234yf. TFPY is toxic and flammable, therefore, improved methods are needed to reduce the amount of TFPY in 1234yf. Summary of the Invention

[0009] In one embodiment, the present invention relates to a method for reducing the concentration of fluorinated alkyne impurities in 2,3,3,3-tetrafluoropropylene (HFO-1234yf); the method comprising contacting a mixture comprising 2,3,3,3-tetrafluoropropylene (HFO-1234yf) and at least one fluorinated alkyne impurity having the formula RC≡CH (where R is a perfluorinated straight-chain C1-C3 alkyl group) with a caustic material under conditions that effectively reduce the concentration of alkyne impurities. Effective conditions include those in which the caustic material forms reaction products with at least some of the alkyne impurities and HFO-1234yf remains substantially unreacted. "Substantially unreacted" as used herein means that at least 90% by weight of HFO-1234yf has not reacted with the caustic material. The reaction products can then be removed, reducing the concentration of alkyne impurities in HFO-1234yf. In one practice, the fluorinated alkyne impurity is TFPY. Caustic materials that can be used in the present invention include, but are not limited to, alkali metal hydroxides, alkali metal oxides, alkaline earth metal hydroxides, alkaline earth metal oxides, and combinations thereof. In a preferred embodiment, the caustic material is sodium hydroxide (NaOH). The concentration of fluorinated alkyne impurities is reduced by at least about 20% (w / w); in another embodiment, the concentration of fluorinated alkyne impurities is reduced by at least about 50% (w / w).

[0010] In a preferred embodiment, the present invention relates to a method for reducing the concentration of 3,3,3-trifluoropropyne (TFPY) in 2,3,3,3-tetrafluoropropene (HFO-1234yf), comprising (a) providing a first composition comprising 2,3,3,3-tetrafluoropropene (HFO-1234yf) and a first concentration of 3,3,3-trifluoropropyne (TFPY); (b) contacting the first composition with a caustic material under conditions that effectively react the caustic material with at least a portion of the TFPY; and (c) recovering a second composition comprising 1234yf and a second concentration of TFPY, the second concentration being less than the first concentration. In one practice, the first concentration of TFPY is greater than 300 parts per million parts by weight (ppm), and the second concentration of TFPY is 300 ppm or less. In other practices, it is 200 ppm or less; preferably 100 ppm or less. Attached Figure Description

[0011] Attached Figure Figure 1 The diagram illustrates the decrease in TFPY concentration over time at 25°C using 4% NaOH (w / w) as a caustic material in one embodiment of the present invention. Detailed Implementation

[0012] The entire contents of U.S. Patent 8,058,486 are incorporated herein by reference. The operations described below may be performed in continuous, semi-continuous, or intermittent methods, or any combination thereof.

[0013] In one embodiment, the present invention provides a method for reducing the concentration of fluorinated alkyne impurities in 2,3,3,3-tetrafluoropropylene (HFO-1234yf), comprising contacting a mixture comprising 2,3,3,3-tetrafluoropropylene (HFO-1234yf) and at least one fluorinated alkyne impurity having the formula RC≡CH (where R is a perfluorinated straight-chain C1-C3 alkyl group) with a caustic material under conditions that effectively reduce the concentration of the alkyne impurities. The conditions cause a reaction product to form between the caustic material and the alkyne impurity, while HFO-1234yf remains substantially unreacted and substantially intact. The reaction product can be removed to further separate HFO-1234yf with improved purity. The term "reaction product" includes, but is not limited to, one or more products formed by contacting the caustic material with the alkyne impurity as described herein, including, but not limited to, decomposition products or other one or more products formed by contacting the caustic material, such as NaOH, with the alkyne, such as TFPY. As used herein, the term "linear perfluorinated alkyl" refers to a linear alkyl group in which all hydrogen atoms on the carbon atoms of the alkyl group are replaced by fluorine. Examples of linear perfluorinated alkyl groups include -CF3, -CF2CF3, and -CF2CF2CF3. In a preferred practice, the perfluorinated alkyl group is -CF3, i.e., the perfluorinated alkyne impurity is 3,3,3-trifluoropropyne (TFPY).

[0014] Non-limiting, in one practice, the initial concentration of fluorinated alkyne impurities in the mixture is greater than about 400 ppm, although other initial concentrations, including those below 400 ppm, are considered. Contact can be accomplished in ways known in the art, including, for example, by directly adding a caustic material to the composition consisting of HFO-1234yf and the fluorinated alkyne impurities; other contact methods include passing the composition, in vapor form, containing HFO-1234yf and the fluorinated alkyne impurities through a reaction vessel or reactor containing the caustic material. HFO-1234yf with a reduced concentration of fluorinated alkyne impurities can be recovered by conventional methods, such as by phase separation when the caustic material is directly added to the composition containing HFO-1234yf and the fluorinated alkyne impurities; and by compression or condensation when the composition consisting of HFO-1234yf and the fluorinated alkyne impurities is passed as a mixed vapor through the caustic material. Optionally, other purification methods, such as distillation, can then be applied to further improve the purity of HFO-1234yf.

[0015] The caustic material may include, for example, alkali metal hydroxides, alkali metal oxides, alkaline earth metal hydroxides, alkaline earth metal oxides, and combinations thereof. Non-limiting examples of suitable alkali metal hydroxides include potassium hydroxide (KOH), sodium hydroxide (NaOH), lithium hydroxide (LiOH), cesium hydroxide (CsOH), rubidium hydroxide (RbOH), and combinations thereof. Non-limiting examples of alkaline earth metal hydroxides include magnesium hydroxide (Mg(OH)2), calcium hydroxide (Ca(OH)2), strontium hydroxide (Sr(OH)2), barium hydroxide (Ba(OH)2), and combinations thereof. A representative non-limiting example of an alkaline earth metal oxide is calcium oxide (CaO). In a preferred embodiment, the caustic material is NaOH.

[0016] In one practice, effective conditions include, but are not limited to, the presence of the caustic material in an aqueous solution at less than 50% by weight; in one embodiment, the caustic material is present in an aqueous solution at 0.1% to about 20% by weight; in another embodiment, the caustic material is present in an aqueous solution at about 1% to about 10% by weight; in a further embodiment, the caustic material is present in an aqueous solution at about 2% to about 5% by weight; more preferably, the caustic material is present in an aqueous solution at about 4% by weight. Non-limitingly, suitable temperatures for the contact step include about 0°C to about 100°C; in one embodiment, about 10°C to about 80°C; in a further embodiment, about 20°C to about 60°C. Non-limitingly, suitable pressures for the contact step include about 0.1 psig to about 1000 psig; in another embodiment, about 5 psig to about 500 psig; in a further embodiment, about 10 psig to about 100 psig. In one practice, the reaction products between the caustic material and the alkyne impurities can be removed from HFO-1234yf by techniques known in the art, such as phase separation, optionally followed by distillation.

[0017] In one embodiment, the practice of the present invention reduces the concentration of fluorinated alkyne impurities in the mixture by at least about 20%, preferably by at least about 30%, more preferably by at least about 40%, and even more preferably by at least about 50%.

[0018] In another embodiment, the practice of the present invention reduces the concentration of fluorinated alkyne impurities to about 300 ppm or less; in one embodiment, the concentration of fluorinated alkyne impurities is reduced to about 200 ppm or less; in another embodiment, the concentration of fluorinated alkyne impurities is reduced to about 100 ppm or less.

[0019] In another embodiment, the present invention relates to a method for reducing the concentration of 3,3,3-trifluoropropyne (TFPY) in a composition comprising 3,3,3-trifluoropropyne (TFPY) and 2,3,3,3-tetrafluoropropene (HFO-1234yf), comprising (a) providing a first composition comprising 2,3,3,3-tetrafluoropropene (HFO-1234yf) and a first concentration of a fluorinated alkyne impurity, such as 3,3,3-trifluoropropyne (TFPY); non-limitingly, the first concentration of TFPY representing the fluorinated alkyne impurity is greater than 300 ppm, although lower concentrations are considered. The method further comprises (b) contacting the first composition with a caustic material under conditions that effectively react the caustic material with at least a portion of the TFPY; the caustic material, as described above, is provided in the form of an aqueous solution in the weight percentages described below. In one practice, the caustic material comprises NaOH. In another embodiment, NaOH is provided as an aqueous solution having about 0.1 wt% to about 20 wt% NaOH; in another embodiment, NaOH is provided as an aqueous solution having about 1 wt% to about 10 wt% NaOH; in another further embodiment, NaOH is provided as an aqueous solution having about 2 wt% to about 5 wt% NaOH; in another embodiment, NaOH is provided as an aqueous solution having about 4 wt% NaOH. The method further includes (c) recovering a second composition comprising 1234 yf and a second concentration of TFPY, the second concentration being less than the first concentration; non-limitingly, in practices where the first concentration of TFPY is greater than 300 ppm, the second concentration of TFPY is 300 ppm or less; preferably about 200 ppm or less; more preferably about 100 ppm or less.

[0020] The method of the present invention can be used as part of a larger method for preparing compounds, such as 2,3,3,3-tetrafluoropropylene (1234yf). For example, the method of the present invention may involve step (3) of the three-step method for preparing 1234yf as described above. In a preferred embodiment in this respect, for step (3): the HCFC-244bb generated in step (2) is dehydrohalogenated under conditions that efficiently produce 2,3,3,3-tetrafluoropropylene (HFO-1234yf). Preferably, the dehydrohalogenation step comprises a gas-phase or vapor-phase catalytic reaction. The catalytic conversion of HCFC-244bb is carried out under conditions that efficiently dehydrochlorinate HCFC-244bb to produce 2,3,3,3-tetrafluoropropylene (HFO-1234yf). Preferably, the dehydrochlorination of HCFC-244bb is carried out in the vapor phase, more preferably in the vapor phase in a fixed-bed reactor. The dehydrohalogenation reaction can be carried out in any suitable reaction vessel or reactor, but the reaction vessel or reactor should preferably be constructed of a material resistant to the corrosive effects of hydrogen chloride (to the extent that such material is formed under dehydrohalogenation conditions), such as nickel and its alloys, including Hastelloy, Inconel, Incoloy and Monel, or carried out in a vessel lined with a fluoropolymer and may be carried out using one or more tubes containing a dehydrohalogenation catalyst.

[0021] The catalyst may include metal halides, metal halide oxides, neutral (or zero-oxidation-state) metals or metal alloys, or activated carbon in bulk or supported form. When using metal halide or metal oxide catalysts, monovalent, divalent, and trivalent metal halides, oxides, and mixtures / combinations thereof are preferred, more preferably monovalent and divalent metal halides and mixtures / combinations thereof. Component metals include, but are not limited to, Cr. 3+ Fe 3+ Mg 2+ Ca 2+ Ni 2+ Zn 2+ Pd 2+ Li + Na + K + and Cs + The halogen components include, but are not limited to, F. - Cl - ,Br - and I - Examples of available monovalent or divalent metal halides include, but are not limited to, LiF, NaF, KF, CsF, MgF2, CaF2, LiCl, NaCl, KCl, and CsCl. Halogenation treatment can include any treatment known in the art, particularly those using HF, F2, HCl, Cl2, HBr, Br2, HI, and I2 as halogen sources.

[0022] When neutral, i.e., zero valence, metals, metal alloys, and mixtures thereof are used. Available metals include, but are not limited to, Pd, Pt, Rh, Fe, Co, Ni, Cu, Mo, Cr, Mn, and combinations thereof as alloys or mixtures. The catalyst can be supported or unsupported. Examples of available metal alloys include, but are not limited to, SS 316, Monel 400, Inconel 825, Inconel 600, and Inconel 625.

[0023] HCFC-244bb can be introduced into the reactor in pure form, partially purified form, or as part of the reactor effluent from previous steps. HCFC-244bb can optionally be fed with an inert gas diluent, such as nitrogen, argon, etc. In one embodiment of the invention, HCFC-244bb is pre-vaporized or preheated before entering the reactor. Alternatively, HCFC-244bb is vaporized inside the reactor. Available reaction temperatures can be from about 100°C to about 700°C. Preferred temperatures can be from about 150°C to about 600°C, and more preferred temperatures can be from about 200°C to about 550°C. The reaction can be carried out under atmospheric pressure, extra-atmospheric pressure, or vacuum. Vacuum pressure can be from about 5 Torr (0.0966 psia) to about 760 Torr (14.69 psia). The contact time between HCFC-244bb and the catalyst can be from about 0.5 seconds to about 120 seconds, but longer or shorter times can be used.

[0024] In such defluorination embodiments described herein, the conversion rate of HCFC-244bb is at least about 10%, more preferably at least about 20%, and even more preferably at least about 30%. Preferably, in such embodiments, the selectivity for HFO-1234yf is at least about 70%, more preferably at least about 85%, and even more preferably at least about 95%.

[0025] In one embodiment, the process flow can pass through the catalyst bed in a downward, upward, or horizontal direction. It is also advantageous to periodically regenerate the catalyst in situ within the reactor after prolonged use. Catalyst regeneration can be accomplished by any method known in the art, such as using an oxidizing agent, like O2 or chlorine. For example, the catalyst can be regenerated by passing air or nitrogen-diluted air through the catalyst for about 0.5 hours to about 3 days (depending on the reactor size) at a temperature of about 100°C to about 400°C, or in another embodiment, about 200°C to about 375°C. Catalyst regeneration can also involve the use of a reducing agent, such as H2. Other reducing agents include, but are not limited to, NH3 (ammonia), CO (carbon monoxide), and CH4 (methane); mixtures of these can also be used, including mixtures with hydrogen.

[0026] Typically, effluents from the dehydrohalogenation reaction step, including any intermediate effluents that may be present in a multi-stage reactor arrangement, can be treated to achieve the desired degree of separation and / or other treatment. For example, in embodiments where the reactor effluent contains HFO-1234yf, the effluent typically also contains HCl and unreacted HCFC-244bb. Some or substantially all of these components of the reaction products can be recovered by any separation or purification method known in the art, such as neutralization and distillation. The concentration of alkyne impurities, such as TFPY, can be reduced through the practice of the present invention. It is contemplated that unreacted HCFC-244bb can be fully or partially recycled to improve the desired overall yield of CF3CF=CH2(HFO-1234yf). Optionally, hydrogen chloride is then recovered from the products of the dehydrochlorination reaction. The recovery of hydrogen chloride is carried out by conventional distillation, in which it is removed from the distillate.

[0027] Alternatively, HCl can be recovered or removed using water or a caustic scrubber. When using a water extractor, HCl is removed as an aqueous solution. When using a caustic extractor, HCl is removed from the system only as a chloride salt in an aqueous solution.

[0028] In an alternative embodiment of the invention, the dehydrohalogenation of HCFC-244bb can also be accomplished by reacting it with a strong caustic solution, including but not limited to KOH, NaOH, Ca(OH)2, and CaO, at an elevated temperature. This is described in U.S. Patent Publication 2011 / 0270000. In this case, the strength of the caustic solution is about 2% to about 100% by weight, in another embodiment about 5% to about 90% by weight, and in a further embodiment about 10% to about 80% by weight. The molar ratio of the caustic material to HCFC-244bb is preferably about 1:1 to about 2:1, more preferably about 1.1:1 to about 1.5:1, and most preferably about 1.2:1 to about 1.4:1. The reaction can be carried out at a temperature of about 20°C to about 100°C, in another embodiment about 30°C to about 90°C, and in a further embodiment about 40°C to about 80°C. As described above, the reaction can be carried out at atmospheric pressure, extra-atmospheric pressure, or a vacuum. The vacuum pressure can be from about 5 Torr (14.80 psig) to about 760 Torr (29.40 psig). Additionally, a solvent or phase transfer catalyst, such as Aliquat 336, can optionally be used to aid in the dissolution of the organic compound in the caustic solution. This optional step can be carried out using solvents known in the art for the purposes described above. HFO-1234yf can then be recovered from the reaction product mixture consisting of unreacted starting materials and byproducts by any method known in the art, such as extraction and preferably distillation. The mixture of HFO-1234yf and any byproducts is passed through a distillation column. For example, distillation can preferably be carried out in a standard distillation column at atmospheric pressure, extra-atmospheric pressure, or vacuum. Preferably, the pressure is less than about 300 psig, more preferably less than about 200 psig, and most preferably less than 150 psig. The pressure of the distillation column inherently determines the distillation operating temperature. Preferably, in such a defluorination embodiment described in this section, the conversion of HCFC-244bb is at least about 60%, more preferably at least about 75%, and even more preferably at least about 90%. Preferably, in such an embodiment, the selectivity for HFO-1234yf is at least about 70%, more preferably at least about 85%, and even more preferably at least about 95%.

[0029] Unless otherwise indicated, all percentages and ppm are based on weight.

[0030] Furthermore, the terms “caustic” and “caustic material” used in this article are synonymous and can be used interchangeably.

[0031] The following non-limiting embodiments are used to illustrate the present invention. Example

[0032] The above description is merely illustrative and does not limit the scope of the invention.

[0033] Example 1

[0034] Place the TFA (trifluoroacetic acid) / D₂O insert in the NMR tube. Add approximately 1.0 g of DI water, just enough to cover the insert. Record the exact weight of the DI water. Then equilibrate the NMR tube in a temperature bath at 25 °C for approximately 2 minutes. Afterward, using a fine peek tube, slowly bubble a pure sample of 3,3,3-trifluoropropyne (TFPY) gas into the liquid to saturate the water and the headspace above the water. Immediately and tightly cover the NMR tube to prevent any gas escape. 19 The initial concentration of TFPY was determined by 1H NMR analysis at 25 °C (at time t=0). The concentration of dissolved gas was calculated relative to the calibrated TFA / D2O insert. A sample of 44% NaOH solution was then prepared, and approximately 0.1 g of sample was injected into the solution and mixed. This produced approximately 4% NaOH solution by weight. The injection time was recorded and... 19 F NMR analysis of the sample was performed every 5–6 minutes for 1 hour. The concentration of TFPY in 4% NaOH (w / w) solution was measured and plotted, as shown in the attached figure. The attached figure depicts the concentration of TFPY in 4% NaOH solution as a function of time at 25 °C. As shown in the attached figure, the concentration of 3,3,3-trifluoropropyne decreases over time, indicating a reaction between TFPY and HaOH.

[0035] Comparative Example 1

[0036] In Comparative Example 1, 2,3,3,3-tetrafluoropropene (HFO-1234yf) was used instead of 3,3,3-trifluoropropyne. Following the same procedure as described in Example 1, it was found that the concentration of HFO-1234yf in the 4% NaOH (w / w) solution remained constant, indicating that no reaction occurred between HFO-1234yf and NaOH.

[0037] Example 2

[0038] At room temperature, a 1L Tedlar bag was filled with 3,3,3-trifluoropropyne (TFPY) gas and 2.11g of 4% NaOH solution was injected into the bag through a diaphragm. The bag was rotated occasionally to allow the liquid to react for 4 days. The liquid was carefully removed from the bag with a syringe and passed through a calibrated TFA (trifluoroacetic acid) / D2O insert. 19 Analysis was performed using F NMR. The results showed that as the reaction proceeded, the peak at -51.0 ppm (attributable to TFPY) decreased while the peak at -119.9 ppm (attributable to F) decreased. -The increase in the concentration of TFPY indicates that some TFPY has reacted and formed fluoride as one of the reaction products. The integral also shows that the conversion of TFPY to fluoride ions is quantitative. By extending the reaction time to 6 days after the liquid is returned to the bag to ensure complete reaction, the reaction capacity of TFPY in the 4% NaOH (w / w) solution was determined to be approximately 1.7% to 1.8% (w / w) of the amount of 4% NaOH (w / w) solution.

[0039] Example 3

[0040] A 750 g mixture of 1234yf and TFPY (0.5% TFPY) was passed through a gas distributor via a gas distributor to 200 mL of 4% NaOH (w / w) aqueous solution, and the tail gas was collected in a liquid nitrogen trap. The collected material was analyzed by GC and GCMS. The results showed that the concentration of TFPY in 1234yf decreased to approximately 260 ppm and the recovery rate of 1234yf was 99%.

[0041] In another experiment, the same procedure was used, except that a 4% (w / w) KOH aqueous solution was used, and similar results were obtained.

[0042] Example 4

[0043] A 750 g mixture of 1234yf and TFPY (0.5% TFPY) was passed through 210 mL of 4% w / w NaOH aqueous solution via a gas distributor at room temperature and 1 atm, and the tail gas was collected in a liquid nitrogen trap. The collected material was analyzed by GC and GCMS. The results showed that the concentration of TFPY in 1234yf decreased to approximately 20 ppm w / w and the recovery of 1234yf was 99%.

[0044] In another experiment, the same procedure was used, except that a 4% w / w KOH aqueous solution was used, and similar results were obtained.

[0045] Example 5

[0046] A 175 g mixture of 1234yf and TFPY (0.5% w / w TFPY) was passed through a gas distributor via a gas distributor at room temperature and 1 atm, and the tail gas was collected in a liquid nitrogen trap. The collected material was analyzed by GC and GCMS. The results showed that the concentration of TFPY in 1234yf decreased to approximately 75 ppm w / w and the recovery of 1234yf was 99%.

[0047] In another experiment, the same procedure was used, except that a 1% (w / w) KOH aqueous solution was used, and similar results were obtained.

[0048] Example 6

[0049] A 2000 g mixture of 1234yf and TFPY (0.5% w / w TFPY) was passed through 205 mL of 10% w / w NaOH aqueous solution via a gas distributor at room temperature, and the tail gas was collected in a liquid nitrogen trap. The collected material was analyzed by GC and GCMS. The results showed that the concentration of TFPY in 1234yf decreased to 165 ppm w / w and the recovery rate of 1234yf was 98%.

[0050] In another experiment, the same procedure was used, except that a 10% w / w KOH aqueous solution was used, and similar results were obtained.

[0051] This application may include the following implementation schemes.

[0052] 1. A method for reducing the concentration of fluorinated alkyne impurities in 2,3,3,3-tetrafluoropropylene (HFO-1234yf), comprising contacting a mixture comprising HFO-1234yf and at least one fluorinated alkyne impurity having the formula RC≡CH with a caustic material under effective conditions, wherein R is a perfluorinated straight-chain C1-C3 alkyl group, thereby forming at least one reaction product between the caustic material and at least a portion of the alkyne impurity, and thereby HFO-1234yf remains substantially unreacted.

[0053] 2. The method of Scheme 1, further comprising recovering HFO-1234yf having a reduced concentration of the fluorinated alkyne impurity.

[0054] 3. The method of Scheme 1, where R is -CF3.

[0055] 4. The method of Scheme 1, wherein the caustic material is selected from alkali metal hydroxides, alkali metal oxides, alkaline earth metal hydroxides, alkaline earth metal oxides, and combinations thereof.

[0056] 5. The method of Scheme 4, wherein the alkali metal hydroxide is selected from potassium hydroxide (KOH), sodium hydroxide (NaOH), lithium hydroxide (LiOH), cesium hydroxide (CsOH), rubidium hydroxide (RbOH), and combinations thereof.

[0057] 6. The method of Scheme 4, wherein the alkaline earth metal hydroxide is selected from magnesium hydroxide (Mg(OH)2), calcium hydroxide (Ca(OH)2), strontium hydroxide (Sr(OH)2), barium hydroxide (Ba(OH)2) and combinations thereof.

[0058] 7. The method of Scheme 4, wherein the alkaline earth metal oxide is calcium oxide (CaO).

[0059] 8. The method of Scheme 1, wherein the caustic material is present in the aqueous solution at less than about 50% by weight.

[0060] 9. The method of Scheme 8, wherein the caustic material is present in an aqueous solution at about 0.1% by weight to about 20% by weight.

[0061] 10. The method of Scheme 9, wherein the caustic material is present in an aqueous solution at about 1% to about 10% by weight.

[0062] 11. The method of Scheme 10, wherein the caustic material is present in an aqueous solution at about 2% to about 5% by weight.

[0063] 12. The method of Scheme 11, wherein the caustic material is NaOH.

[0064] 13. The method of Scheme 1, wherein the concentration of the fluorinated alkyne impurity is reduced by at least about 20%.

[0065] 14. The method of Scheme 13, wherein the concentration of the fluorinated alkyne impurity is reduced by at least about 30%.

[0066] 15. The method of Scheme 14, wherein the concentration of the fluorinated alkyne impurity is reduced by at least about 40%.

[0067] 16. The method of Scheme 15, wherein the concentration of the fluorinated alkyne impurity is reduced by at least about 50%.

[0068] 17. A method for reducing the concentration of 3,3,3-trifluoropropyne (TFPY) in 2,3,3,3-tetrafluoropropene (HFO-1234yf), comprising:

[0069] (a) Provide a first composition comprising 2,3,3,3-tetrafluoropropylene (HFO-1234yf) and 3,3,3-trifluoropropyne (TFPY) at a first concentration;

[0070] (b) Contacting the first composition with the caustic material under conditions that effectively react the caustic material with at least a portion of the TFPY; and

[0071] (c) Recover a second composition containing 1234yf and a second concentration of TFPY, wherein the second concentration is less than the first concentration.

[0072] 18. The method of Scheme 17, wherein the first concentration of TFPY is greater than 300 ppm.

[0073] 19. The method of Scheme 17, wherein the second concentration of TFPY is 300 ppm or less.

[0074] 20. The method of scheme 19, wherein the second concentration of TFPY is about 200 ppm or less.

[0075] 21. The method of scheme 20, wherein the second concentration of TFPY is about 100 ppm or less.

[0076] 22. The method of Scheme 17, wherein the caustic material comprises NaOH.

[0077] 23. The method of Scheme 22, wherein NaOH is provided as an aqueous solution having about 0.1 wt% to about 20 wt% NaOH.

[0078] 24. The method of Scheme 23, wherein NaOH is provided as an aqueous solution having about 1% to about 10% by weight of NaOH.

[0079] 25. The method of Scheme 24, wherein NaOH is provided as an aqueous solution having about 2% to about 5% by weight of NaOH.

[0080] 26. The method of Scheme 24, wherein NaOH is provided as an aqueous solution having about 4% by weight of NaOH.

Claims

1. A method for reducing the concentration of 3,3,3-trifluoropropyne (TFPY) in 2,3,3,3-tetrafluoropropene (HFO-1234yf), comprising: (a) Provide a first composition comprising 2,3,3,3-tetrafluoropropylene (HFO-1234yf) and 3,3,3-trifluoropropyne (TFPY) at a first concentration; (b) Contact the first composition with a caustic material under conditions that effectively react the caustic material with at least a portion of the TFPY, thereby reducing the concentration of TFPY, wherein the caustic material is NaOH; and (c) Recover a second composition containing 1234yf and a second concentration of TFPY, wherein the second concentration is less than the first concentration; It also includes the dehydrochlorination of HCFC-244bb under conditions that effectively produce the first composition provided in step (a).

2. The method according to claim 1, wherein the dehydrochlorination of HCFC-244bb is carried out in a gas-phase reactor.

3. The method according to claim 1, further comprising reacting 2-chloro-3,3,3-trifluoropropene (1233xf) with HF under conditions that effectively generate HCFC-244bb.

4. The method of claim 3, wherein the reaction of 2-chloro-3,3,3-trifluoropropene (1233xf) with HF occurs in a liquid-phase reactor containing a liquid catalyst to produce HCFC-244bb.

5. The method according to claim 3, further comprising reacting 1,1,2,3-tetrachloropropene (1230xa) with hydrogen fluoride (HF) under conditions that effectively generate 2-chloro-3,3,3-trifluoropropene (1233xf).

6. The method according to claim 5, wherein the reaction of 1,1,2,3-tetrachloropropene with hydrogen fluoride (HF) occurs in a gas-phase reactor containing a solid catalyst.

7. A method for reducing the concentration of fluorinated alkyne impurities in 2,3,3,3-tetrafluoropropylene (HFO-1234yf), comprising: HCFC-244bb is dehydrochlorinated under conditions that effectively produce a mixture containing HFO-1234yf and at least one fluorinated alkyne impurity having the formula RC≡CH, wherein R is a perfluorinated straight-chain C1-C3 alkyl group. The mixture is brought into contact with a caustic material under conditions that effectively reduce the concentration of the at least one fluorinated alkyne impurity, thereby forming at least one reaction product between the caustic material and at least a portion of the alkyne impurity, and thereby HFO-1234yf remains substantially unreacted, wherein the caustic material is NaOH.

8. The method of claim 7, wherein the concentration of fluorinated alkyne impurities is reduced by at least 20%.

9. The method of claim 8, wherein the concentration of fluorinated alkyne impurities is reduced by at least 30%.

10. The method of claim 9, wherein the concentration of fluorinated alkyne impurities is reduced by at least 40%.

11. The method of claim 10, wherein the concentration of fluorinated alkyne impurities is reduced by at least 50%.

12. The method of claim 7, further comprising the step of reacting 2-chloro-3,3,3-trifluoropropene (1233xf) with HF to produce HCFC-244bb.

13. The method of claim 12, wherein the reaction of 2-chloro-3,3,3-trifluoropropene (1233xf) with HF occurs in a liquid-phase reactor containing a liquid catalyst to produce HCFC-244bb.

14. The method of claim 13, further comprising the step of: 1,1,2,3-Tetrachloropropene (1230xa) is reacted with HF in a gas-phase reactor containing a solid catalyst to produce 2-chloro-3,3,3-trifluoropropene (1233xf).

15. The method of claim 7, wherein HCFC-244bb is dehydrochlorinated in the gas phase under conditions that effectively generate HFO-1234yf.

16. A method for preparing 2,3,3,3-tetrafluoropropylene (HFO-1234yf), comprising: The method according to any one of claims 7 to 15 reduces the concentration of fluorinated alkyne impurities in HFO-1234yf.

17. The method of claim 16, further comprising the step of reacting 2-chloro-3,3,3-trifluoropropene (1233xf) with HF to produce HCFC-244bb.

18. The method of claim 17, wherein the reaction of 2-chloro-3,3,3-trifluoropropene (1233xf) with HF occurs in a liquid-phase reactor containing a liquid catalyst to produce HCFC-244bb.

19. The method of claim 18, further comprising the step of: 1,1,2,3-Tetrachloropropene (1230xa) is reacted with HF in a gas-phase reactor containing a solid catalyst to produce 2-chloro-3,3,3-trifluoropropene (1233xf).

20. The method of claim 16, wherein the dehydrochlorination of HCFC-244bb occurs in the gas phase under conditions that effectively generate HFO-1234yf.

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